Single pulping system for multiple pulp stocks used in paperboard machine

ABSTRACT

Various pulp stocks which are to be used in the formation of various layers of multilayered paperboard are prepared by sequential passage of each stock through a single pulping system which includes a pulper, a liquid cyclone, a centrisorter, and pulp thickeners, prior to storage in separate storage tanks. Stocks from the different tanks can be withdrawn and blended in multiple blend chests (with appropriate additive chemicals also being added to the blend chests) for passage to separate stock drop chests and formation points on the paperboard machine.

United States Patent 1 [111 3,833,465

Campbell Sept. 3, 1974 SINGLE PULPING SYSTEM FOR MULTIPLE FOREIGN PATENTS OR APPLICATIONS PULP STOCKS USED IN PAPERBOARD 859,646 l/l96l Great Britain [62/125 MACHINE 557,691 12/1943 Great Britain l62/l87 [75] Inventor: Hubert J. Campbell, Trenton,

Ontario, Canada Primary Examiner-S. Leon Bashore Assistant ExaminerRichard l-l. Tushin [73] Asslgnee' $rg gg gg iib g' g gg Attorney, Agent, or FirmStevens, Davis, Miller &

Mosher [22] Filed: Apr. 27, 1971 21 Appl. No.: 137,788 [571 ABSTRACT Various pulp stocks which are to be used in the formation of various layers of multilayered paperboard are [52] Cl 7 5 47 1 i prepared by sequential passage of each stock through [51] Int Cl D21 d 6 D21 5 /28 Dzlf 11/04 a single pulping system which includes a pulper, a liq- [58] Field 162/1OO 380 131 uid cyclone, a centrisorter, and pulp thickeners, prior 162/129 L 2 to storage in separate storage tanks. Stocks from the different tanks can be withdrawn and blended in multiple blend chests (with appropriate additive chemicals [56] References cued also being added to the blend chests) for passage to UNITED STATES PATENTS separate stock drop chests and formation points on 1,483,149 2/1924 Witham 162/380 X the paperboard machine. 2,151,357 3/1939 Reitzel 162/123 X i 3,301,745 5 Claims, 2 Drawing Figures 1/1967 Coppick et al. 162/55 -TH/CKENERS a Q I0 I I 6b 80 f -FILTRATE THICK STOCK CHEST 55 TANK I 0 /0a I [60 I6d a l6)! /2 12a 12b [24 2 /2r )5 I50 I56 '56 5d Pmmww W4 I mamss SHEfi 2 0F 2 DYE STORAGE I60 16b /6 lg we 25 TANK n v g lar 26 I v sTARcH STORAGE mm A r a 3 390 v v 4/0 38 1 39b 45a 43a Burro/w 42 TOP LINER 4 LINER CHEST CHEST I 44 45 401/ 39c 45 3 W v 39b 390 V 4/19 44 FILLER BOTTOM TOP 450 LINER LINER 45 CHEST 43 CHEST 44 CHEST FIG; IA.

SINGLE PULPING SYSTEM FOR MULTIPLE PULP STOCKS USED IN PAPERBOARD MACHINE The present invention relates to the production of paperboard (boxboard) and in particular relates to an improved method and apparatus for the preparation of liner pulp stocks (also referred to herein as liner stocks) for feeding to the paperboard machine in the production of paperboardl Paperboard conventionally comprises one or more liners (layers), each liner being formed from a liner pulp stock of different fiber, quality, type or composition. Thus for example a typical paperboard may consist of a top liner and a bottom liner between which is a filler liner and there may also be present an underliner between the filler liner and the top liner. Economically it is desirable to form the paperboard of the cheapest cellulosic fibrous pulp available, such pulp being secondary fiber pulp obtained by repulping waste cellulosic fibrous material such as waste paper and paperboard. However, the paperboard obtained is of poor quality, inter alia in appearance, and it is conventional to form the paperboard from a plurality of liners, the outer liners e. g., the top and bottom liners, being formed primarily from better quality pulps and, in particular from blends of secondary fiber and virgin wood pulps, whereas the filler liners and the underliners are formed from liner stock formed primarily from secondary fiber pulps. In particular it is conventional to form the top liner primarily from high grade liner pulp stock, e.g., virgin wood pulp stock with the blending with the virgin wood pulp stock of increasing amounts of lower grade wood pulp stock in forming the bottom liner and the underliners to the point where the filler liner is substantially low grade pulp fibers, e.g., secondary pulp fibers.

In the formation of the paperboard, a liner pulp stock of the required pulp fiber grade is fed continuously to a required point on the paperboard machine such as a Fourdrinier or Cylinder paperboard machine from a separate liner chest through a Jordan headbox. ,The amount of liner stock in each liner chest be it the tiller liner chest, the bottom chest, the top liner chest or the underliner chest is conventionally maintained individually. Thus in conventional methods the different liner pulp stocks to be fed to the paperboard machine are each made by an individual pulping and blending system. For example, for a paperboard machine producing paperboard having four liners, namely a top liner, underliner, bottom liner and filler, four complete pulper systems are present to convert the furnish e.g., virgin wood pulp or the secondary fibers into liner pulp stock. Each liner pulp stock is then fed directly to a selected one of four points on the paperboard machine to produce the paperboard. Each pulper system includes a pulper, a cyclone type cleaner, a pressure screen, vibrating screen, such as a Jonsson screen, and a thickener in addition to ancillary equipment such as pumps, meters, consistency regulators and dump and machine chests. All of the foregoing are expensive items of equipment and further require substantial labour in their operation. Further, with the conventional system the capacity of the liner stock preparation equipment is substantially identical to the production capacity of the paperboard machine and, therefore, when the paperboard machine is stopped, the preparation of the liner pulp stock for the machine also has to be stopped.

Conversely, if any one of the liner pulp stock preparation systems breaks down, then the paperboard machine must also stop after using up a residual small amount of liner pulp stock in the chests. Again, the preparation of the liner stocks takes place primarily in the pulper with the dry weight of the different furnishes necessary to form the liner pulp stock being estimated as the furnishes are put into the pulper. This provides for a margin of error in proportioning of the various ingredients into the pulper depending upon the operator. Thus, the preparation of the liner stock is subject to individual error with the result that a non-uniform liner stock pulp is easily produced.

The present invention provides a process for producing liner stock for feeding to a conventional paperboard machine, which process may be operated with a single pulp preparation system with a consequent substantial saving of capital equipment and labour in the production of the paperboard, which method allows for accurate and uniform blending of the liner stock, which I process has increased flexibility of operation allowing for breakdown and maintenance of the pulp preparation system and the paperboard machine without the stoppage of one of the systems causing stoppage of the other, and which process may be operated substantially completely automatic. v

It has now been found according to the present invention that the above advantages may be achieved by separating the pulping and blending stages in the preparation of the liner'stocks, whereby each liner stock is prepared by blending pulp stocks of different fiber grade from separate storage tanks, the pulp stocks having been separately prepared from different furnishes and supplied to said tanks.

According to the present invention therefore there is provided in the production of paperboard, having a plurality of liners of different pulp fiber grade which comprises for at least some of the liners, pulping and blending a plurality of furnishes of different fiber grade to form a liner stock and feeding each liner stock to a selected point on a paperboard machine, the improvement which comprises separately pulping furnishes of different pulp fiber grade to form a plurality of separate pulp stocks and blending at least two of said pulp stocks to form each of said liner stocks.

The present invention also provides an apparatus for use in the production of liner stocks for separate delivery to a paperboard machine to fomi a plurality of liners in the paperboard obtained, said apparatus comprising a pulper adapted to pulp furnish to form a pulp stock, a plurality of storage tanks, each tank being adapted to receive pulp stock of a different pulp fiber grade from said pulper, and blending means adapted to blend the pulp stock withdrawn from at least two of said storage tanks to form said liner stocks.

The pulp stocks are suitably prepared by conventional methods involving pulping the furnish in a conventional pulper, such as a hydrapulper, to a selected consistency, cleaning and refining the pulp, thickening the cleaned and refined pulp to the consistency required by the paperboard machine and passing the pulp stock to one of a plurality of storage tanks. It will be seen that by separation of the pulping and blending stages, a single pulping system may be used to supply pulp stock of different fiber grade to each of the storage tanks and at the same time maintain the storage tanks full of the relative pulp stock. Further, as the blending takes place with wet pulp stock, accurate and automatic blending of the pulp stocks may be achieved to form the liner stock thus eliminating the human error which has previously, occurred in the conventional process.

The blending of the pulp stocks to form the liner pulp stock is suitably effected by metering the pulp stocks from at least two of the storage tanks, suitably by means of magnetic flow meters, into a collecting trough through which the mixed pulp stocks together with any chemical additives, which may also be metered into the collecting trough, are passed to a blending tank for the preparation of the required liner stock for feeding to the paperboard machine. It will be realized that for some of the liners, particularly the filler liner, blending of the pulp stocks may not be necessary, in which case pulp stock would only be withdrawn from one of the storage tanks and blended with the required chemical additives; However, even with the filler liner stock blending is usually necessary. After blending in the blending tank the blended pulp stocks are suitably passed to drop tanks for the Jordan headboxes on the conventional paperboard machine with any further blending of the blended pulp stocks, particularly for the top liner stock, taking place in the drop chests.

The present invention will be further illustrated by way of the accompanying drawing in which F I68. 1 and 1A are a schematic representation of the process and apparatus in accordance with the preferred embodiment of the present invention, for producing liner stocks for use in a pair of conventional paperboard machines.

Referring to FIGS. 1 and 1A, furnish in the form of dry fiber bundles is fed to a pulper 1 via a conveyor 2. The pulper 'l is of sufficient size and is suitably an- 18 foot Fleck pulper equipped with a Vokes rotor and inch screen plates. Pulping in the pulper l is continuous and pulp stock at 2 percent consistency is continuously pumped from the pulper l by pump 3 via lines 1a and 3a to a dump chest 4 where the pulp stock is stored and diluted to approximately 0.8 to 1.0 percent consistency. Pulp stock is pumped by pump 5 from the chest 4 via lines 4a and Sa'to a liquid cyclone 6 for cleaning thereof, the liquid cyclone 6, suitably taking the form of a battery of seven 12 inch centrifugal cleaners equipped with fibermisers. For further cleaning the pulp stock is passed from the cyclone 6,via line 6a to a centrisorter (or pressure screen) 7 from whence it passes via line 7a to a pair of thickeners 8 in the form of deckers which serve to thicken the pulp stock to 4 percent consistency which consistency is suitable for the paperboard machine. The rejects from the centrisorter 7 are diluted and passed via line 7b to a vibrating screen 9, e.g., a Fink or Jonsson screen, from which the accepts are returned via line 9a to the pulper l.

The thickened pulp stock from the thickeners 8 is dropped via lines 8a to a thick stock chest 10 from whence it is pumped by pump 11 via lines 100 and 11a to selected one of a plurality, e.g., seven, storage chests 12, 12a, 12b, 12c, 12d, 12e and'12f. The white water from the thickeners 8 is passed through lines 8b to a filtrate chest 13 from whence it is pumped by pump 14 via lines l3-and l4ato the pulper l for further use in pulping, part of the white water being recycled to the thickener 8 via line 14b and part to the dump chest 4 via line 140 for cleaning purposes. Storage tanks 12-12f thus hold pulp stocks'of different pulp fiber grade from which pulp stock blends for forming the liner pulp stocks can readily be formulated. The storage tanks 12-121" are supplied from a single pulper l in a single pulping stock preparation system, the quantity of pulp stock in each of the storage tanks 1242f being maintained as required by supplying the appropriate furnish to the pulper 1.

From the storage tanks 12-12f the pulp stock is pumped by pumps l5-l5f via lines l6-l6f and magnetic flow meters 17 to a collecting trough 18 from whence the mixed pulp stock passes to the required blend chest, i.e., the'filler blend chest 19, the liner blend chest 20 or the white liner blend chest 21, via lines 22, 23 and 24 respectively. During mixing of the pulp stocks in the collecting trough l8 chemical addition is made and in particular dye is fed thereto from storage tank 25 by pump 26 via line 27 and magnetic flow meter 28, starch is fed thereto from storage tanks andalum is fed thereto from storage tank 33 by pump 34 via line 35 and magnetic flow'meter 36.

When the different types of pulp stock and chemicals are properly blended in the chests 19 to 21 the blended pulp stock is pumped from chest 19 via pump 37 and lines 37a containing valves 37)) to a pair of filler liner drop chests 38. The blended stock from chest 20 is pumped by pump 39 via line 39a and valve 39b to a pair of bottom liner drop chests 40 and the blended stock is pumped from chest 21 by pump 41 via lines 41a through valves 41b to a pair of top liner drop chests 42, the drop chests 42 also being fed with some of the blended pulp stock from chest 20 via lines 390 and valves 39d connected to lines39a. From each group of dropchests 38, 40 and 42 the liner stocksare pumped by pumps 43, 44 and 45 respectively via lines 43a, 44a and 45a to headboxes (not shown) suitably Jordan headboxes one of a pair of conventional paperboard machines such as Fourdrinier or Cylinder machines. It is pointed out that each paperboard machine is a conventional paperboard machine and in no way forms part of the present invention and such a machine has not been described herein.

While the present invention has been specifically described with respect to the production of paperboard having three liners, namely the bottom liner, filler liner and top liner, the apparatus and method of the present invention may be readily adapted to produce paperboard with more liners, e.g., including an underliner by the addition of appropriate blending chests and drop chests and if necessaryfurther storage tanks.

The'operation of the process may be controlled from a central control panel which automatically controls the flow of pulp stock to and from the storage tanks 12-l2f from the timethe material handler places the dry raw furnish on the conveyor 1. Thus the magnetic flow meters 17, 28, 32 and 36 may be programmed to automatically meter to a predetermined recipe. The control panelmay be operated by a computer if desired or it can be operated manually by an operator who sets up the desired sequence, quantity and order of mixing by means of a series of push buttons on a console. The operator can observe the entire process on a graphic panel which depicts each piece of equipment and which indicates the flow of pulp stock on a series of panel lights set into miniature replicas.

It will be seen that the critical feature of the present invention is the presence of the storage tanks 12-12f which separate the fonnation of the pulp stock from the blending of the pulp stock to form the liner pulp stock and, as such, the preparation of the pulp stock is independent of the subsequent blending allowing for a single pulp preparation system to be used to prepare the blends of different pulp fibers required for each liner pulp stock and this provides a substantial saving in capital equipment over the conventional system where a separate pulp preparation system is required for the preparation of each of the liner stocks. Thus one pulper provides the pulp stock requirements of all the liners of the paperboard for two or more machines and replaces eight conventional pulper lines in a two paperboard machine mill. As such the labour requirements are substantially reduced, and in particular are reduced from ten people, namely a foreman, eight operators and a material handler for the conventional process to three men, namely a control panel operator, a lead hand and a material handler. Further, provided the capacity of the storage tanks is sufficiently large, paperboard production can be substantially improved and allow for either the paperboard machine or the pulping system to shut down for repairs or maintenance and, in particular it will be readily seen that even with the paperboard machine shut down the production of the pulp stock can still continue in the pulp preparation system and vice versa with pulp preparation system shutdown, the paperboard machine can still draw from the pulp stock in the storage tanks. Thus, the process of the present invention has improved flexibility. Still further the wet pulp stock from the storage tanks can be accurately proportioned automatically for blending with respect to the different grades of pulp fibers and chemical additives, which proportioning may be accurately repeated providing uniform liner stock which is not subject to human variation and' error.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In the production of paperboard having a plurality of liners of different pulp fiber grade which comprises for at least some of the liners, pulping and blending a plurality of furnishes of different fiber grade to form a liner pulp stock and feeding each liner stock to a selected point on a paperboard machine, the improvement which comprises:

1. separately pulping each of said plurality of furnishes in the same single pulp preparation system by first passing a furnish selected from said plurality of furnishes to a single pulping mechanism, and then cleaning the pulp stock formed in said mechanism from said furnish, then thickening said pulp stock to the required consistency for use in said paperboard machine, and passing said pulp stock to a separate storage tank;

2. repeating the steps of subparagraph (1) for a plurality of said furnishes thereby providing a plurality of different pulp stocks in a plurality of separate storage tanks; and

withdrawing and blending pulp stock from at least two of said storage tanks, passing each blend from said blending of pulp stocks from said storage tanks to a separate blend chest and withdrawing blended stock from each of said blend chests and passing it to separate liner stock drop chests with, where required, mixing of the blended stocks to form each liner stock in said drop chests.

2. A process as claimed in claim 1 in which additive chemicals are introduced into the liner pulp stocks during blending of the pulp stocks.

' 3. A process as claimed in claim 1 in which three liner stocks are prepared to produce a paperboard having a top liner, filler liner and bottom liner.

4. A process as claimed in claim 1 in which four liner stocks are prepared to produce a paperboard having a top liner, underliner, filler liner and bottom liner.

5. Apparatus for use in the production of liner stocks for separate delivery to a paperboard machine for forming a plurality of liners in the paperboard obtained from said machine, said apparatus comprising: a single pulp preparation system comprising a single pulper mechanism, means for cleaning pulp, and a pulp thickener, serially connected to each other; a plurality of storage tanks, each tank connected for separately receiving a pulp stock of different fiber grade from said single pulp preparation system; collecting means for receiving and mixing pulp stocks of different grades from at least two of said storage tanks, separate blend chests for receiving mixtures from said collecting means and for blending pulp stocks for forming blended stocks of different fiber grades, and drop chests for receiving blended stocks from said blend chests for forming said liner stocks.

UNITED STATES PATENT ND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3 I 833 I 465 DATED 1 September 3, 1974 INVENTOR(S I Hubert J. CAMPBELL It is certified that error appears in the ab0veidentified patent and that said Letters Patent are hereby corrected as shown below:

Please capitalize the word "Centrisorter" in line 5 of the Abstract of the- Disclosure, and thereafter insert (registered trademark of the Bird Machine Co.

Column 3, lines 48 and 52, "centrisorter" should be capitalized.

Signed and Sealed this thirteenth Day of April 1976 [SEAL] A ttes t:

RUTH C. MASON C. MARSHALL DANN Arresting Officer (mnmissiom'r 01' Patch and Trademarks j UNITED STATES PATENToFF ICE CERTIFICATE OF CORRECTION =Patent No. 3,833,465 Dated September 3, 1974 fle) Hubert J CAMPBELL It is certified thaterror appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The Assignee of the above-idehftified patent is:

The Miller Bros. co.; (1962). Limited,

Trenton, Ontario.

(SEAL) Attest:

McCOY 2-1. GIBSON JR. Attesting Officer c. MARSHALL TDANN Commissioner of Patents FORM PO-105O (to-69) r US'COMWDC wan-PM \LLGQVIRNHINT PRINTING OIIICE: I0! 0-36-33-3. 

2. A process as claimed in claim 1 in which additive chemicals are introduced into the liner pulp stocks during blending of the pulp stocks.
 2. repeating the steps of subparagraph (1) for a plurality of said furnishes thereby providing a plurality of different pulp stocks in a plurality of separate storage tanks; and withdrawing and blending pulp stock from at least two of said storage tanks, passing each blend from said blending of pulp stocks from said storage tanks to a separate blend chest and withdrawing blended stock from each of said blend chests and passing it to separate liner stock drop chests with, where required, mixing of the blended stocks to form each liner stock in said drop chests.
 3. A process as claimed in claim 1 in which three liner stocks are prepared to produce a paperboard having a top liner, filler liner and bottom liner.
 4. A process as claimed in claim 1 in which four liner stocks are prepared to produce a paperboard having a top liner, underliner, filler liner and bottom liner.
 5. Apparatus for use in the production of liner stocks for separate delivery to a paperboard machine for forming a plurality of liners in the paperboard obtained from said machine, said apparatus comprising: a single pulp preparation system comprising a single pulper mechanism, means for cleaning pulp, and a pulp thickener, serially connected to each other; a plurality of storage tanks, each tank connected for separately receiving a pulp stock of different fiber grade from said single pulp preparation system; collecting means for receiving and mixing pulp stocks of different grades from at least two of sAid storage tanks, separate blend chests for receiving mixtures from said collecting means and for blending pulp stocks for forming blended stocks of different fiber grades, and drop chests for receiving blended stocks from said blend chests for forming said liner stocks. 